Marissa Mayer’s brief maternity leave: Progress or workaholism?

FORTUNE — Yahoo CEO Marissa Mayer will likely have the most scrutinized maternity leave and new motherhood in modern corporate history, which began on Sunday night with the birth of a healthy baby boy.

Mayer courted controversy by deciding to take just a week or two of leave and work from home throughout that time.

On one hand, it’s a remarkable sign of gender progress that a new mother is now at the helm of a major corporation — not to mention reassuring to Yahoo YHOO shareholders that the CEO’s top priority is turning around the struggling Internet giant.

On the other hand, her decision seems emblematic of a workaholic culture that leaves too little time for family or even personal health, preventing either men or women from “having it all.”

Could Mayer be setting unrealistic expectations for young women hoping to follow in her footsteps?

Maybe she’s an outlier — or making a mistake — and shouldn’t be held up as an example that mere mortals should emulate.

“She conveys the image of someone who’s perfectly capable of combining her personal life and her public responsibilities without one derailing the other. That’s a message we should applaud,” says Kathleen Gerson, professor at New York University and author of The Unfinished Revolution: Coming of Age in a New Era of Gender, Work and Family. “It also suggests that somehow it’s illegitimate for women — and by implication for men as well — to take some time off at critical moments in their own lives and the lives of their children. To that extent, it’s a backward-looking message.”

It’s difficult to judge whether Mayer’s abbreviated maternity leave plan will make it harder or easier for the millions of executive women who will follow her, certainly at this early stage. But there are three indisputable lessons that can be drawn from her situation.

Women can be both CEOs and mothers

We already know from Hewlett-Packard’s hpq Meg Whitman, Facebook’s fb Sheryl Sandberg, and a handful of other C-level executive moms that women can indeed combine motherhood with a rise to the top ranks of corporate America. However, the fact that the Yahoo board put Mayer into the CEO spot when she was expecting her first child hammers home that message.

“It is extraordinarily awesome that the board went for it. Good for the board,” says Cali Williams Yost, flexible work strategy consultant and author of Tweak It: Make What Matters to You Happen Every Day. “It’s a great moment where that was not a hurdle.”

Sociological researchers have documented that women face a “motherhood penalty” of lower earnings and slower advancement after they have children, either because of outright discrimination or assumptions by managers that mothers won’t want more demanding assignments. The Yahoo board’s decision to forge ahead despite Mayer’s pregnancy suggests that they are “evolved,” as Mayer herself put it.

“There’s nothing about being a woman that disqualifies you from doing all that,” Gerson says. “Being pregnant and giving birth is not a disease. It’s a natural part of life.”

Indeed, Mayer’s story may be an opportunity to debunk the notion that successful workers never need time off, whether for medical situations, childbirth, or family needs. A male CEO could require hernia surgery or experience a heart attack, after all, Gerson notes.

It’s good to have options; Mayer may have more than most

Just because Mayer feels capable of taking scant maternity leave doesn’t mean that other women should feel obliged to work through birth and new motherhood — or that their employers should expect it. “It shouldn’t be a bar now that everybody is gauged against,” Yost says. “Her circumstances are really unique. She has a very big job she chose to take.”

Another thing to keep in mind: As a multi-millionaire CEO married to Silicon Valley investor Zachary Bogue, Mayer has resources that the rank-and-file can’t tap. She has the money to hire a squadron of nannies, maids, cooks, and other household help that would make life easier for any new parent. She also has the authority to bring her baby to work or to change her schedule if she chooses.

“CEOs have flexibility that assembly line workers don’t have,” says Ellen Galinsky, president and co-founder of the Families and Work Institute. “I wish we wouldn’t see her as the ultimate role model for the new woman. Right now, she’s mainly speaking to her stockholders and her company.”

There are many low-income workers who take only a few weeks of unpaid maternity leave because they can’t afford more, not because they choose to be back at work so soon after giving birth. “What they would give to be in a situation [where] they had the financial resources” to take longer leave, says Brad Harrington, director of the Center for Work and Family at Boston College.

Mayer couldn’t please all parties

To be fair, Mayer probably would have been disparaged no matter what decision she made about her maternity leave.

“If she takes time off, then the question raised is, ‘How can you do this just as you’re taking over this company?’ ” Gerson says. “If she doesn’t, then she’s criticized for being unrealistic, for not attending to her newborn child’s needs, for setting the wrong example for other women. It’s hard to imagine what decision she could have made that would not have been seen through a controversial lens.”

Advocates for workplace flexibility say the real landmark moment would be if a male CEO decided to take several months of paternity leave after the birth of a new child. Harrington notes that the majority of men take off less than two weeks for a child’s birth.

“If a man could set an example that it’s important to take time to be with a newborn — not to mention your children at any age — that would send a much more straightforward message,” Gerson says. “What we need are more people, especially men, who can make that counterintuitive and somewhat braver choice: to give family the equal place it deserves, even in the highest levels of the economy.”

Galinsky will be watching carefully to see how Mayer’s plans for a brief maternity leave evolve and not only what example she sets, but her explicit messages and policies for the Yahoo workforce around parental and medical leave. “I would be very worried if she didn’t figure out ways to encourage other women and men who work for Yahoo to take leave,” she says.